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Java I/O Q&A » serialize » class 

1. Why its required to mark a class as serializable?

If a similar question is already posted on stackoverflow, pls just post the link. What is the need to implement Serializable interface (with no methods) for objects which are to be serialized ...

2. How to send a Class over the wire

I have the following problem: I want to send a type (java.lang.Class) over the wire and 'define' the class on the other side. I tried like that:

ByteArrayOutputStream bos = new ByteArrayOutputStream();
ObjectOutputStream oos ...

3. Java serialization problem

I would like to change my qestion to the following: I have one HashMap object, and one int. I want to serialize the into the same file and get back. I know ...

4. Why is this class not Serializable?

I was using the Mersenne-Twister implementation at as a drop-in replacement for the default java.util.Random class. However, four fields (an int, a boolean and two byte[]) are marked ...

5. Converting Serialized Java Classes Between XML and Binary

I am using Java native serialization along with a dynamic proxy to save the parameters and returns of a series of method calls to a file. I would like to convert the ...

6. Serialization third-party classes with Simple XML (org.simpleframework.xml)

I have decided to use Simple XML serialization and was stucked with basic problem. I am trying to serialize java.util.UUID class instance as final field in this small class:

public ...

7. how to test in Java that a class implements Serializable correctly (not just is an instance of Serializable)

I am implementing a class to be Serializable (so it's a value object for use w/ RMI). But I need to test it. Is there a way to do this easily? clarification: ...

8. How can I change package for a bunch of java serializable classes

I want to change the packages of multiple classes in my application. A nice eclipse redactor good have been great but some of my classes are Serializables and I need to support ...

9. Is it safe to use bytecode enhancement techniques on classes that might be serialized and why?

I haven't tried this yet, but it seems risky. The case I'm thinking of is instrumenting simple VO classes with JiBX. These VOs are going to be serialized over ...

10. Class serialization in simple program, should I worry about it?

Im working on a very simple project in java that utilizes the Swing component and I have a class that when finished with all its statements, Eclipse underlines it with a yellow ...

11. Java serialization, UID not changed. Can I add new variables and method to the class?

Hi I have a class that is serialised. Now I need to add a new variable into the class, with setter and getter methods. This class is sent over ...

12. Why not serialize abstact classes in Java?

I have read that generally abstract classes should not be made Serializable in Java. The subclasses should be serializable (with custom read, write methods if required, for eg. when abstract classes ...

13. problem in loading class from 'me.prettyprint.hector.api.Serializer'

I have created executable jar but having some problem with Class not found Exception. When I type command: java -jar JarFileName.jar arguments.. I get error message,

Exception in thread "main" java.lang.NoClassDefFoundError: me/prettyprint/hector/api/Serializer

14. Replacing class name in serialized data

I want to replace the String "com.oldpackage.className" with "com.newPackage.className" in a stream of serialized data. This serialized data is read from the DB and updated after replacing the string. I am facing ...

15. How to create inner children without creating another class?

I need to generate an XML like this:

The simplest solution is creating an inner class on the Root class:
class ...

16. What is the significance of class?

In "Layman's" terms I was wondering if someone could explain to me the significance and general importance of importing the Serializable class to implement the interface. asked from java student ...

17. How to remove the dependency on a Java enum's values?

[Mind the gap: I know that the best solution would be to get rid of the enum completely, but that's not an option for today as mentioned in the comments, but ...

18. Extended a Serializable Class, how to use in Remote-Calls?

Here's my situation: I have a server application, providing a remote interface which uses bean objects as call parameters / return values. These are of course Serializable. For instance, a Doctor, that ...

19. Serializable classes and the == operator

Here is the source code of the String.equals method:

public boolean equals(Object anObject) {
    if (this == anObject) {
        return true;

20. Class not serializable after methods are overridden

I override a createSocket() method in my test cases to pas in a mocked Socket. After doing this the objects aren't serializable anymore. Here's a example of what doesn't work.


public ...

21. Why is a serializable inner class not serializable?

The following code:

public class TestInnerClass {

public static void main(String[] args) throws IOException {
    new TestInnerClass().serializeInnerClass();

private void serializeInnerClass() throws IOException {
    File file = new File("test");

22. Loading serialized classes

What is the easiest way to load a class that has been serialized using the standard Java Serialization API? Is there any trivial relationship between the .class format and the serialized form ...

23. Why this class not serializable?

I have error: Type '$$EnhancerByCGLIB$$2f6af516' was not included in the set of types which can be serialized by this SerializationPolicy or its Class object could not be loaded. For security purposes, ...

24. What happens if class is not serialized?

If a class does not implement the Serializable interface, can a program save its state using serialization?

25. Adding parameterless constructor to non-serializable, extendable class

What is special about addid a parameterless constructor to a non serializable, extendable class. In Effective java , the author talks about this topic.

Naively adding a parameterless constructor and a ...

26. Custom class Serializable Dynamic Class Loading

I have a simple custom object like this. import; public class TestObject implements Serializable { private String name; private String city; public String getCity() { return city; } public void setCity(String city) { = city; } public String getName() { return name; } public void setName(String name) { = name; } } I want to send it across ...

27. Serialization & Predefined Primitive Classes

OK. So here is a snippet of code that demonstrates this problem. When running, you need to pass a file name to serialize to. Thanks. -matthew CODE SNIPPET ----------------------- import; import; import; import; import; public class PrimitiveSerialization { public static void main(String[] args) { Object primitiveClass = Integer.TYPE; if (args.length > 0) { File file = ...

28. problem with using serializable class

Hello, i'm using a servlet on my server and a applet that communicate with the servlet to request/reponse data. i've got a problem with sending a serializable class because although in the servlet's jar and the applet's jar there is the class of the serialized object when trying writing object method to translate it back to and obj he can't find ...

29. Inner class & serialize

Ok my fault, my meaning was : A inner class can not be serialized (ad deserialized) because a no static inner calss can not have static members (and for serilize a class needs a public static final long verionUI).The code below argue this. public class SerilizeInnerClass { private final String fileName = "out.buff"; public SerilizeInnerClass() { System.out.println("Serialize start"); serialize(); System.out.println("Serialize end"); ...

30. Serialization vs Properties Class

I need some advice as to which way I should go in either seializing an object and writing it to a database (blobs) or use a Propertis class and store collection key value pairs and store that in the database, some how. now if someone can give me some advice on strengths or weaknesses of either approach I will be really ...

31. Extend Non-Serializable class and implements Serializable - Abnormal

I wanted to try to extend a non seriazable class, and using the extended class by implements serializable interface instead of using transient keyword, as says by an SCJP 1.5 book certification, that it can be done..I could, but end with some exception. Here is the list of classes and output (below). Why ? import*; class Collar1 { private int ...

32. serialization of subtypes of a serializable class

The doc under Serializable interface states that "All subtypes of a Serializable class are themselves serializable." But, i also find that the class javax.servlet.http.HttpServlet is declared to implement the Serializable interface even though its super class javax.servlet.GenericServlet is Serializable. I am curious to know if is there any reason why a subtype could be declared as serializable when the super class ...

33. Serializing protected variable from super class

Hello, I have these classes class javax.mail.URLName{ //does not implement serializable protected String fullUrl; //won't serialize because class is not serializable } I need to serialize URLName, in particular the fullUrl field. However, I am subclassing it, and the subclass DOES implement serializable. class URL extends javax.mail.URLName implements{} My question is: When I serialize URL (sub-class of URLName), will the ...

36. Class serialization

Hello people, is there any solution how to serialize the class in runtime ? For example, if I have class A and I want to serialize new A().getClass(), then I get something, but not exactly the class bytes. I do testing of a custom classloader that does bytecode modification. I want to compare the initial class and loaded class. Daniel.

37. A nested class serialization.

Hi, First, I'm quite new in Java, so my questions might look a bit stupid. I've tried to search the forum, but couldn't find the case that I'm interested in (or simply didn't understand the explanation ). The problem: I'm writing a Java TCP thread (RedHead linux machine) which is supposed to send a data (originally a large number of the ...

38. Serialization Failing with Incompatiable class

Hi Friends, I have an class which implements serializable.i have made some changes and redeployed but its giving me the InvalidClassException.incompatiable Classes and diffrent serialversioUID in the stream class and local class. I have added the serialversionUID in the log which shown and its working fine. the same serialVersionUID would works for all envn.because i have tried in my QA ...

39. Problem with serializing a class

Hi, Could anybody look at the codes below and tell me where I have gone wrong.I am experimenting with the ObjectOutputStream.I have a class student whose state I want to serialize(in class testfile) and deserialize (in class custom ).Output .....only first record is written moreover when I adding true in construction of ObjectOutputStream then nothing is written. why??? Thanks in adv ...

40. Re: Serializable Class

41. serializable class

Serializable is a 'tag' interface - it has no methods to implement. It is just used to indicate that a class can be serialized (in some cases you specifically DONT want them to be serializable, which is why classes are not serializable by default). This short example writes out an instance of a Person object to a file on disk. It ...

42. Removing a method from a Serializable class

Does removing a method break serialization? I ran into a class that implements Serializable. It doesn't declare a version uid. It seems like the application is throwing an InvalidClassException after removing a method, although the method is unused. I am wondering if this is the reason why I am getting the error or something else might have triggered it.

43. Does an inner class inherit it's encapsulating class's serialization?

In this example: public class Foo implements Serializable { private List miniFoos; private class MiniFoo { private String a; private String b; public MiniFoo(String a, String b) { setA(a); setB(b); } public void setA(String a) { this.a = a } public void setB(String b) { this.b = b; } } public void addFooBaby(String a, String b) { MiniFoo mini = new ...

44. cannot change a non serializable class which has no no-arg constructor

Hi All, I know that this is quite an old problem and comes up all the time, but I could not really find the solution so far. So, what can I do if I'd like to re-use a class which is not serializable but does not have a no-arg constructor and I need to make the subclass serializable? E.g. the class ...

45. Serializing a class in Java

46. not serializable error after implemaenting inteface on a particula class

class BaseFile{ static ArrayList store=null; public static void load(){ FileOutputStream in=new FileOutputStream("test.txt"); ObjectOutputStream out=new ObjectOutputStream(in); out.WriteObject(store); out.close(); } public class Dairy extends BaseFile { public Dairy(){ if(store==null){ store=new ArrayList(); } BufferedReader br = new BufferedReader(new InputStreamReader(; public static void main(String args[]) { String name = null; String dob = null;eader(new InputStreamReader(; System.out.println("enter name"); name = br.readLine(); System.out.println("enter dob"); System.out.println("enter dob in ...

47. My serialization class - warning

Hi, I wrote class to write and read serialization objects. I used generalized types but i had one warning whose i don't understand. Code: import; import; import; import; import; import; class ObjectSerialization { public static T readObject(String name) { T object = null; try { FileInputStream fileInputStream = new FileInputStream(name); ObjectInputStream objectInputStream = new ...

48. Unable to serialize a class

I am getting a NotSerializableException while running the following code.The error comes due to the line "Tree tree = new Tree();".. However if i stop making the object of Tree class at that point and simply write "Tree tree;", no exception is thrown.. I am not able to understand why it is not possible to Serialize that way? public class Forest ...

49. how makeChild classes as Non Serializable if parent class is Serializable in java ?

However, even if the sub class is Serializable (capital S, instance of the interface) it doesn't need to be serializable (lowercase s, can actually be serialized). If an instance has any non-transient fields that are not serializable then the instance is not serializable - trying to serialize it will lead to an IOException.

50. Serialization of Derived classes

Hello, I am trying to send via server - serialized classes problem is i got one base class and 10 derived classes from it. now, when i do deserialization of "Derived class 2" how do i know what to cast it back in the client ? it can by any of the 10 Derived or even the Base itself. thanks

51. Trouble with on class that is serialized

Trouble with on class that is serialized So I'm doing a simple course database program, where I have a database object that includes arraylists of differents objects, like course and educator class objects, and a gui created using breezyswing. Now the problem is, that every time I use my course editing class, which itself works fine, and try ...

52. serializing super class

53. serializable: How to make sure all the classes are tested?

kdGreg, I looked at emma's sample report. Do you know , out of the three you mentioned here, which can help my case. I mean, Which can tell me that, "Class A is serialized but Class B is not, hence Class B will fail if you try to run"? Go this question after looking at emma page, emma doesn't seem to ...

54. Serialization and Non-serial super class

Hi, I have a typical scenario of having a serial class and its non serial super class. I am saving the non serial super class fields along with those of the serial class fields by having a writeObject/readObject method pair in the serial class. One thing I am not being able to find out why the following is happening: 1> I ...

55. Abstract + Concrete classes & Serializable

56. Serialization and Class Integration

I have a class that I want to serialize in order to save it to a file. In terms of OO design what is the best way to go about integrating serialization into my classes? I was going to have two static methods that would read/write an object of the class from/to a stream, where both the stream and object are ...

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